The present invention relates generally to a tractortowed implement arrangement, and more particularly to an improved interface system for connecting the hydraulic lift cylinder of a towed implement to a tractor hitch control system.
As shown in U.S. Pat. No. 4,518,044 issued 21 May, 1985 to Wiegardt et al., hitch control systems for controlling tractor hitch mechanisms are well known. Typically, an implement such as a plow is integrally coupled to the hitch draft links so that variations in hitch position and/or draft force are sensed by an electronic control unit. The control unit, in turn, supplies control signals to a hitch control valve which controls fluid flow to a hitch cylinder which adjusts the vertical position of the hitch in response to the changes in the sensed position or sensed draft force. As shown in U.S. Pat. No. 3,627,053 issued 14 Dec., 1971 to Hook et al., a hydromechanical system is known wherein the hitch control valve and a selector valve controls a remote cylinder of a towed implement. Another hydromechanical control system for a hitch cylinder and a towed implement cylinder is shown in U.S. Pat. No. 2,974,733 issued 14 Mar. 1961 to Fletcher. However, with these prior art systems the operator may have to first undertake to raise the hitch to its extreme top position to ensure that the hitch does not interfere with the tongue of the towed implement. Also, these earlier systems do not easily provide for non-closed loop control of the remote cylinder independent of the hitch control valve.